Xanthurenic acid derivative pharmaceutical compositions and methods related thereto

ABSTRACT

The present invention relates to diuretic pharmaceutical compositions and methods and in particular to certain derivatives of the formula I: 
     
       
         
         
             
             
         
       
         
         
           
             or a prodrug or pharmaceutically acceptable salt thereof; and 
             a pharmaceutically acceptable carrier.

RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 12/642,743, filed Dec. 18, 2009, now issued U.S. Pat. No.8,034,576, which is a continuation of U.S. patent application Ser. No.11/323,580, filed Dec. 29, 2005, abandoned, which is acontinuation-in-part of U.S. application Ser. No. 11/027,131, filed Dec.29, 2004, pending. The entire contents of each of these applications areincorporated herein by reference.

BACKGROUND OF THE INVENTION

Diuretics are a group of drugs used to treat a variety of medicalconditions, including congestive heart failure, hypertension, certaintypes of liver and kidney diseases and increased intra-ocular pressure.Diuretics act on the transport of sodium (Na⁺) by the nephrons of thekidney so as to increase the renal excretion of Na⁺ (and associatedions) and water out of the body and thereby to decrease theextracellular fluid (ECF) volume. Normally, Na⁺ enters the ECF via thediet, and is excreted in the urine in amounts identical to the intake.In normal adults over 99% of the sodium entering the nephrons of the twokidneys (via glomerular filtration) is transported via an energydependent process out of the tubular fluid and back into the ECF. Whenthis balance between intake and excretion is upset (with excretionfalling below intake) salt retention will occur. A primary mechanism oftreating this abnormality involves the administration of one or moreagents that reduce Na⁺ and water reabsorption by the kidneys and therebyincrease their excretion in the urine. These agents, collectively, areknown as diuretics. Optimally, a powerful diuretic should be natriuretic(inhibit resorption of sodium ions) but not kaliuretic (inhibitresorption of potassium ions) since potassium loss is an undesirableside effect. The principle drugs which are included in the “diuretic”category act by inhibiting the transport of Na⁺ (and water) out of thetubular fluid by acting on a specific “carrier” in the tubularepithelial cells at a specific site of the nephron. The latter varieswith the diuretic employed.

Several major classes of diuretics exist including loop diuretics,thiazide-type diuretics and potassium-sparing diuretics. Loop diuretics,also known as high-ceiling diuretics, act on the thick ascending loop ofHenle within the kidney. Examples include furosemide, bumetanide andtoresemide. Loop diuretics have a peak diuretic effect far greater thanother classes of diuretics. This class acts to inhibit electrolytereabsorption resulting in the excretion of not only sodium, but alsopotassium, calcium and magnesium. Loop diuretics are considered“potassium wasting.” For example, furosemide is commonly used to treatheart failure, pulmonary edema, hypertension and poisoning.Unfortunately, if dietary potassium is not sufficient, hypokalemia mayresult and this may induce cardiac arrythmias (Goodman and Gilman's ThePharmacological Basis for Therapeutics, 10th Ed.; Hardman, Limbird &Gilman, Eds, MacGraw-Hill, p. 772, 2001).

Thiazide-type diuretics act in the distal tubule and connecting segmentof the kidneys. Examples include chlorothiazide, chlorthalidone,hydrochlorothiazide, indapamide and metolazone. Although thiazides causeless distortion of the electrolyte composition of the extra-cellularfluid than other classes of diuretics, there is also lower intensity ofdiuresis produced by these drugs. This class contains many sulfonamidechemical entities and thus may cause an allergic reaction in those withsulfa allergies. Although thiazides do not cause calcium excretion,potassium excretion increases with acute administration. Thiazides mayalso induce hyperglycemia and aggravate pre-existing diabetes mellitus.Thiazide diuretics may also cause increased serum cholesterol,low-density lipoprotein (LDL) and triglyceride concentration. Thiazidesare also considered “potassium wasting” diuretics.

Potassium-sparing diuretics may act through either of severalmechanisms. Some are steroidal in structure and act inaldosterone-sensitive cells in the cortical connecting tubule in thekidney. Members in this drug class are competitive antagonists ofendogenous mineralocorticoid steroids such as aldosterone, which acts toenhance sodium absorption and potassium excretion. The aldosteronereceptor is a soluble, cytoplasmic protein found in several tissuesincluding salivary glands, colon and segments of nephrons in the kidney.Spironolactone, a representative member of this drug class, binds to thealdosterone receptor and prevents the receptor from assuming an activeconformation. Spironolactone also increases calcium excretion. Commonside-effects includes nausea, stomach cramps and diarrhea. Other sideeffects involve endocrine imbalances, gynecomastia (abnormal enlargementof one or both breasts in men), altered libido, impotence or hirsutism(excessive body hair). Triamterene and amiloride are non-steroidalpotassium-sparing diuretics that inhibit electrogenic entry of sodium inthe late segments of the kidney nephron. Triamterene and amiloride causean increase in sodium and chloride excretion, but have little effect onpotassium excretion. Side effects of Triamterene include hyperkalemia(increased serum potassium concentration), nausea, vomiting, leg crampsand dizziness. Amiloride side effects also include hyperkalemia, nausea,vomiting, diarrhea and headache.

Other classes of diuretics include osmotic diuretics and carbonicanhydrase inhibitors. Osmotic diuretics, such as mannitol, are poorlyreabsorbed by the renal tubules. This drug class effects poor netreabsorption of sodium salts. In addition, mannitol is poorly absorbedby the gastrointestinal tract, and thus must be administeredintravenously. Other osmotic diuretics include glycerol, urea andisosorbide.

Carbonic anhydrase inhibitors, such as acetazolamide, cause a modestdecrease of sodium reabsorption and may also cause loss of potassium andmetabolic acidosis due to its mechanism of action.

Diuretics are used to treat high blood pressure (hypertension), eitheralone, or in combination with other drugs. High blood pressure adds tothe workload of the heart and arteries. If the condition continues for aprolonged period of time, heart and artery function may be impaired.This can damage the blood vessels of the brain, heart and kidneys,resulting in stroke, heart or kidney failure. High blood pressure mayalso increase the risk of heart attack. These risks can be reduced ifblood pressure is properly controlled. The National Heart, Lung, andBlood Institute's (NHLBI) high blood pressure guidelines (JAMA, May 21,2003) emphasize a need to develop new diuretic medications without theside affects of the aforementioned diuretic pharmacopeia.

SUMMARY OF THE INVENTION

A pharmaceutical composition comprising a therapeutically effectiveamount of a compound of formula I:

wherein R₁, R₂, R₃, R₅, R₆ and R₇ are independently X₃R where R isselected from the group consisting of H, halo; optionally substitutedsaccharide, aliphatic, cycloalkyl, heterocycloalkyl, aryl andheteroaryl; —P(O)(OR^(a))(OR^(b)) and —NR^(a)R^(b), where R^(a) andR^(b) are independently H, optionally substituted aliphatic, cycloalkyl,heterocycloalkyl, aryl or heteroaryl;

X₁, X₂ and X₃ are independently —C(O)O—, —OC(O)—, —C(O)NH—, —NHC(O)—,—OC(O)NH—, —NHC(O)O—, —OS(O)_(y)—, —S(O)_(y)—, —O—, —NHC(O)—, —NHC(O)O—,—S(O)₂NH—, a bond or absent; where y is an integer from 0 to 3; and

R₄ and R₈ are independently H, (═O); hydroxy; or optionally substitutedsaccharide, aliphatic, cycloalkyl, heterocycloalkyl, aryl or heteroaryl;or —P(O)(OR^(a))(OR^(b)) or —NR^(a)R^(b), where R^(a) and R^(b) areindependently H, or optionally substituted aliphatic, cycloalkyl,heterocycloalkyl, aryl or heteroaryl; or

a prodrug or pharmaceutically acceptable salt thereof; and

a pharmaceutically acceptable carrier.

The present invention also provides methods of treating, controlling andpreventing hypertension, edema, acute renal failure, congestive heartfailure, chronic renal failure, ascites, increased intra-ocular pressureor nephrotic syndrome and other related diseases and conditions usingpharmaceutical compositions comprising compounds of formula I.

A BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows Na⁺ urine excretion in response to intravenous (i.v.)administration (2 μg dose) of synthetic xanthurenic acid8-O-β-D-glucoside in a normal Sprague Dawley rat.

FIG. 2 shows Na⁺ and K⁺ urine excretion in response to i.v.administration (2 μg dose) of synthetic xanthurenic acid8-O-β-D-glucoside in a normal Sprague Dawley rat.

FIG. 3 shows Na⁺ and K⁺ concentration in urine following i.v.administration (2 μg dose) of synthetic xanthurenic acid8-O-β-D-glucoside in a normal Sprague Dawley rat.

FIG. 4 shows urine volume following i.v. administration (2 μg dose) ofsynthetic xanthurenic acid 8-O-β-D-glucoside in a normal Sprague Dawleyrat.

FIG. 5 shows Na⁺ excretion in response to i.v. administration (10 μgdose) of synthetic xanthurenic acid 8-O-β-D-glucoside in a normalSprague Dawley rat.

FIG. 6 shows Na⁺ and K⁺ urine excretion in response to i.v.administration (10 μg dose) of synthetic xanthurenic acid8-O-β-D-glucoside in a normal Sprague Dawley rat.

FIG. 7 shows Na⁺ and K⁺ concentration in urine in response to i.v.administration (10 μg dose) of synthetic xanthurenic acid8-O-β-D-glucoside in a normal Sprague Dawley rat.

FIG. 8 shows urine volume following i.v. administration (10 μg dose) ofsynthetic xanthurenic acid 8-O-β-D-glucoside in a normal Sprague Dawleyrat.

FIG. 9 shows Na⁺ urine excretion in response to synthetic xanthurenicacid 8-O-β-D-glucoside (10 μg) followed by furosemide (100 μg) in anormal Sprague Dawley Rat, oral (p.o.) administration.

FIG. 10 shows Na⁺ and K⁺ urine excretion in response to syntheticxanthurenic acid 8-O-β-D-glucoside (10 μg) followed by furosemide (100μg) in a normal Sprague Dawley Rat, oral (p.o.) administration.

FIG. 11 shows Na⁺ and K⁺ concentration in urine in response to syntheticxanthurenic acid 8-O-β-D-glucoside (10 μg) followed by furosemide (100μg) in a normal Sprague Dawley Rat, oral (p.o.) administration.

FIG. 12 shows urine volume following administration of syntheticxanthurenic acid 8-O-β-D-glucoside (10 μg) followed by furosemide (100μg) in a normal Sprague Dawley Rat, oral (p.o.) administration.

FIG. 13 shows Na⁺ urine excretion in response to isolated xanthurenicacid 8-O-β-D-glucoside (3 ug) followed by furosemide (20 μg) in a uremicSprague Dawley rat, i.v. administration.

FIG. 14 shows Na⁺ and K⁺ urine excretion in response to isolatedxanthurenic acid 8-O-β-D-glucoside (3 μg) followed by furosemide (20 μg)in a uremic Sprague Dawley rat, i.v. administration.

FIG. 15 shows Na⁺ and K⁺ urine concentration in urine in response toisolated xanthurenic acid 8-O-β-D-glucoside (3 μg) followed byfurosemide (20 μg) in a uremic Sprague Dawley rat, i.v. administration.

FIG. 16 shows urine volume in response to isolated xanthurenic acid8-O-β-D-glucoside (3 μg) followed by furosemide (20 μg) in a uremicSprague Dawley rat, i.v. administration.

FIG. 17 shows Na⁺ urine excretion in response to isolated xanthurenicacid 8-O-sulfate (2 μg) in uremic Sprague Dawley rat, i.v.administration.

FIG. 18 shows Na⁺ and K⁺ urine excretion in response to isolatedxanthurenic acid 8-O-sulfate (2 μg) in uremic Sprague Dawley rat, i.v.administration.

FIG. 19 shows Na⁺ and K⁺ urine concentration in urine in response toisolated xanthurenic acid 8-O-sulfate (2 μg) in uremic Sprague Dawleyrat, i.v. administration.

FIG. 20 shows urine volume in response to isolated xanthurenic acid8-O-sulfate (2 μg) in uremic Sprague Dawley rat, i.v. administration.

FIG. 21 shows Na⁺ urine excretion in response to synthetic xanthurenicacid 8-O-sulfate (20.0 ug) in normal Sprague Dawley rat by oraladministration.

FIG. 22 shows Na⁺ and K⁺ urine excretion in response to syntheticxanthurenic acid 8-O-sulfate (20.0 ug) in normal Sprague Dawley rat byoral administration.

FIG. 23 shows Na⁺ and K⁺ concentration in urine in response to syntheticxanthurenic acid 8-O-sulfate (20.0 ug) in normal Sprague Dawley rat byoral administration.

FIG. 24 shows urine volume in response to synthetic xanthurenic acid8-O-sulfate (20.0 ug) in normal Sprague Dawley rat by oraladministration.

FIG. 25 shows Na⁺ and K⁺ urine excretion in normal Sprague Dawley rat inresponse to, furosemide (0.5 mg, i.v.).

FIG. 26 shows urine excretion rate of normal Sprague Dawley rat inresponse to furosemide (0.5 mg i.v.).

DETAILED DESCRIPTION OF THE INVENTION

As used herein, the following definitions shall apply unless otherwiseindicated.

The phrase “optionally substituted” is used interchangeably with thephrase “substituted or unsubstituted.” Unless otherwise indicated, anoptionally substituted group may have a substituent at eachsubstitutable position of the group, and each substitution isindependent of any other. Also, combinations of substituents orvariables are permissible only if such combinations result in stablecompounds. In addition, unless otherwise indicated, functional groupradicals are independently selected. Where “optionally substituted”modifies a series of groups separated by commas (e.g., “optionallysubstituted A, B or C”; or “A, B or C optionally substituted with”), itis intended that each of the groups (e.g., A, B and C) is optionallysubstituted.

The term “aliphatic” or “aliphatic group” as used herein means astraight-chain or branched C₁₋₁₂ hydrocarbon chain that is completelysaturated or that contains one or more units of unsaturation, or amonocyclic C₃₋₈ hydrocarbon or bicyclic C₈₋₁₂ hydrocarbon that iscompletely saturated or that contains one or more units of unsaturation,but which is not aromatic (also referred to herein as “carbocycle” or“cycloalkyl”), that has a single point of attachment to the rest of themolecule wherein any individual ring in said bicyclic ring system has3-7 members. For example, suitable alkyl groups include, but are notlimited to, linear or branched or alkyl, alkenyl, alkynyl groups andhybrids thereof such as (cycloalkyl)alkyl, (cycloalkenyl)alkyl or(cycloalkyl)alkenyl.

The terms “alkoxy,” “hydroxyalkyl,” “alkoxyalkyl” and “alkoxycarbonyl,”used alone or as part of a larger moiety include both straight andbranched chains containing one to twelve carbon atoms. The terms“alkenyl” and “alkynyl” used alone or as part of a larger moiety shallinclude both straight and branched chains containing two to twelvecarbon atoms.

The terms “haloalkyl,” “haloalkenyl” and “haloalkoxy” means alkyl,alkenyl or alkoxy, as the case may be, substituted with one or morehalogen atoms. The term “halogen” or “halo” means F, Cl, Br or I.

The term “heteroatom” means nitrogen, oxygen, or sulfur and includes anyoxidized form of nitrogen and sulfur, and the quaternized form of anybasic nitrogen. The term “aryl” used alone or in combination with otherterms, refers to monocyclic, bicyclic or tricyclic carbocyclic ringsystems having a total of five to fourteen ring members, wherein atleast one ring in the system is aromatic and wherein each ring in thesystem contains 3 to 8 ring members. The term “aryl” may be usedinterchangeably with the term “aryl ring”. The term “aralkyl” refers toan alkyl group substituted by an aryl. The term “aralkoxy” refers to analkoxy group substituted by an aryl.

The term “heterocycloalkyl,” “heterocycle,” “heterocyclyl” or“heterocyclic” as used herein means monocyclic, bicyclic or tricyclicring systems having five to fourteen ring members in which one or morering members is a heteroatom, wherein each ring in the system contains 3to 7 ring members and is non-aromatic.

The term “heteroaryl,” used alone or in combination with other terms,refers to monocyclic, bicyclic and tricyclic ring systems having a totalof five to fourteen ring members, and wherein: 1) at least one ring, inthe system is aromatic; 2) at least one ring in the system contains oneor more heteroatoms; and 3) each ring in the system contains 3 to 7 ringmembers. The term “heteroaryl” may be used interchangeably with the term“heteroaryl ring” or the term “heteroaromatic”. Examples of heteroarylrings include 2-furanyl, 3-furanyl, N-imidazolyl, 2-imidazolyl,4-imidazolyl, 5-imidazolyl, 3-isoxazolyl, 4-isoxazolyl, 5-isoxazolyl,2-oxadiazolyl, 5-oxadiazolyl, 2-oxazolyl, 4-oxazolyl, 5-oxazolyl,1-pyrrolyl, 2-pyrrolyl, 3-pyrrolyl, 1-pyrazolyl, 3-pyrazolyl,4-pyrazolyl, 2-pyridyl, 3-pyridyl, 4-pyridyl, 2-pyrimidyl, 4-pyrimidyl,5-pyrimidyl, 3-pyridazinyl, 2-thiazolyl, 4-thiazolyl, 5-thiazolyl,5-tetrazolyl, 2-triazolyl, 5-triazolyl, 2-thienyl, 3-thienyl,carbazolyl, benzimidazolyl, benzothienyl, benzofuranyl, indolyl,quinolinyl, benzotriazolyl, benzothiazolyl, benzooxazolyl,benzimidazolyl, isoquinolinyl, indazolyl, isoindolyl, acridinyl, andbenzoisoxazolyl. The term “heteroaralkyl” refers to an alkyl groupsubstituted by a heteroaryl. The term “heteroarylalkoxy” refers to analkoxy group substituted by a heteroaryl.

An aryl (including aralkyl, aralkoxy, aryloxyalkyl and the like) orheteroaryl (including heteroaralkyl, heteroarylalkoxy and the like)group may contain one or more substituents. Suitable substituents on theunsaturated carbon atom of an aryl, heteroaryl, aralkyl or heteroaralkylgroup are selected from halogen; haloalkyl; —CF₃; —R⁹; —OR⁹; —SR⁹;1,2-methylenedioxy; 1,2-ethylenedioxy; protected OH (such as acyloxy);phenyl (Ph); Ph substituted with R⁹; —O(Ph); —O-(Ph) substituted withR⁹; —CH₂(Ph); —CH₂(Ph) substituted with R⁹; —CH₂CH₂(Ph); —CH₂CH₂(Ph)substituted with R⁹; —NO₂; —CN; —NR⁹R¹⁰; —NR⁹C(O)R¹⁰; —NR⁹C(O)NR¹⁰R¹¹;NR⁹CO₂R¹⁰; —NR⁹NR¹⁰C(O)R¹¹; —NR⁹—NR¹⁰C(O)NR¹¹R¹²; —NR⁹NR¹⁰CO₂R¹¹;—C(O)C(O)R⁹; —C(O)CH₂C(O)R⁹; —CO₂R⁹; —C(O)R⁹; —C(O)NR⁹R¹⁰; —OC(O)NR⁹R¹⁰;—S(O)₂R⁹; —SO₂NR⁹R¹⁰; —S(O)R⁹; —NR⁹SO₂NR¹⁰R¹¹; —NR⁹SO₂R¹⁰; —C(═S)NR⁹R¹⁰;—C(═NH)—NR⁹R¹⁰; —(CH₂)_(y)NHC(O)R⁹; —(CH₂)_(y)R⁹; —(CH₂)_(y)NHC(O)NHR⁹;—(CH₂)_(y)NHC(O)R⁹; —(CH₂)_(y)NHS(O)R⁹; —(CH₂)_(y)NHSO₂R⁹; or—(CH₂)_(y)NHC(O)CH((V)_(z)—R⁹)(R¹⁰) wherein R⁹, R¹⁰, R¹¹ and R¹² areindependently selected from hydrogen, optionally substituted C₁₋₆aliphatic, an unsubstituted 5-6 membered heteroaryl or heterocyclicring, phenyl (Ph), —O(Ph) or —CH₂(Ph)-CH₂(Ph), wherein y is 0-6; z is0-1; and V is a linker group. When R⁹, R¹⁰, R¹¹ or R¹² is C₁₋₆aliphatic, it may be substituted with one or more substituents selectedfrom —NH₂, —NH(C₁₋₄ aliphatic), —N(C₁₋₄ aliphatic)₂, —S(O)(C₁₋₄aliphatic), —SO₂(C₁₋₄ aliphatic), halogen, (C₁₋₄ aliphatic), —OH,—O—(C₁₋₄ aliphatic), —NO₂, —CN, —CO₂H, —CO₂(C₁₋₄ aliphatic), —O(haloC₁₋₄ aliphatic), or —halo(C₁₋₄ aliphatic); wherein each C₁₋₄ aliphaticis unsubstituted.

An aliphatic group or a non-aromatic heterocyclic ring may contain oneor more substituents. Suitable substituents on the saturated carbon ofan alkyl group or of a non-aromatic heterocyclic ring are selected fromthose listed above for the unsaturated carbon of an aryl or heteroarylgroup and the following: ═O, ═S, ═NNHR¹³, ═NNR¹³R¹⁴, ═N—, ═NNHC(O)R¹³,═NNHCO₂(alkyl), ═NNHSO₂(alkyl), or ═NR¹³, where R¹³ and R¹⁴ areindependently selected from hydrogen and an optionally substituted C₁₋₆aliphatic. When R¹³ or R¹⁴ is C₁₋₆ aliphatic, it may be substituted withone or more substituents selected from —NH₂, —NH(C₁₋₄ aliphatic),—N(C₁₋₄ aliphatic)₂, halogen, —OH, —O—(C₁₋₄ aliphatic), —NO₂, —CN,—CO₂H, —CO₂(C₁₋₄ aliphatic), —O(halo C₁₋₄ aliphatic) or -halo(C₁₋₄aliphatic); wherein each C₁₋₄ aliphatic is unsubstituted.

Substituents on the nitrogen of a non-aromatic heterocyclic ring areselected from —R¹⁵, —NR¹⁵R¹⁶, —C(O)R¹⁵, —CO₂R¹⁵, —C(O)C(O)R¹⁵,—C(O)CH₂C(O)R¹⁵, —SO₂R¹⁵, —SO₂NR¹⁵R¹⁶, —C(═S)NR¹⁵R¹⁶, —C(═NH)NR¹⁵R¹⁶ or—NR¹⁵SO₂R¹⁶; wherein R¹⁵ and R¹⁶ are independently selected fromhydrogen, an optionally substituted C₁₋₆ aliphatic, optionallysubstituted phenyl (Ph), optionally substituted —O(Ph), optionallysubstituted —CH₂(Ph), optionally substituted —CH₂CH₂(Ph), or anunsubstituted 5-6 membered heteroaryl or heterocyclic ring. When R¹⁵ orR¹⁶ is a C₁₋₆ aliphatic group or a phenyl ring, it may be substitutedwith ore or more substituents selected from —NH₂, —NH(C₁₋₄ aliphatic),—N(C₁₋₄ aliphatic)₂, halogen, —(C₁₋₄ aliphatic), —OH, —O—(C₁₋₄aliphatic), —NO₂, —CN, —CO₂H, —CO₂(C₁₋₄ aliphatic), —O(halo C₁₋₄aliphatic) or -halo(C₁₋₄ aliphatic); wherein each C₁₋₄ aliphatic isunsubstituted.

The term “saccharide” defines a carbohydrate, or sugar, made up of oneor more units with the empirical generic formula (CH₂O)_(n). Asaccharide is further classified as a monosaccharide, disaccharide orpolysaccharide depending on the number of units or an aminosaccharide ifone or more oxygen atoms are replaced by a nitrogen atom. A saccharidemay also be classified as a deoxysaccharide if one or more hydroxygroups are replaced by a hydrogen atom.

A saccharide substituent may be further substituted on any primary orsecondary hydroxy group by, for example, an alkyl, alkoxyalkyl, aryl,heteroaryl, ether, ester, acetal, carbonate or carbamate.

The term “monosaccharide” defines a single carbohydrate, or sugar unit.Two families of monosaccharides are aldoses or ketoses. Aldoses have acarbonyl group at the end of the carbon chain as an aldehyde, when themonosaccharide is written in a linear, open-chain formula. If thecarbonyl is in any other position in the carbon chain the monosaccharideis a ketone and referred to as a ketose. Three carbon monosaccharidesare trioses: glyceraldehydes, an aldose, and dihydroxyacetone, a ketose.Monosaccharides, except for dihydroxyacetone, have one or moreasymmetric centers. The prefixes D- or L- refer to the configuration ofthe carbon atom of the chiral carbon most distant from the carbonylcarbon. Monosaccharides with 4, 5, 6 and 7 carbon atoms in theirbackbones are termed tetroses, pentoses, hexoses, and heptoses,respectively. Each of these exists in two series: aldotetroses andketotetroses, aldopentoses and ketopentoses, aldohexoses andketohexoses, aldoheptoses and ketoheptoses. Tetroses include erythroseand threose. Pentoses include ribose, arabinose, xylose and lyxose.Hexoses include allose, altrose, glucose, mannose, gulose, idose,galactose and talose. Monosaccharides with 5 or more carbons in thebackbone usually occur as cyclic, or ring, structures in which thecarbonyl carbon has formed a covalent bond with one of the hydroxygroups along the chain. Six-membered ring compounds are termedpyranoses, five-membered ring compounds are furanoses. Formation of asix-membered ring results from reaction of aldehydes and alcohols toform hemi-acetals which contain an asymmetric carbon atom. Oneconfiguration around the C-1 carbon is described as α- and the other isdescribed as the β-form.

The term “disaccharide” refers to a molecular moiety containing twomonosaccharides covalently bound to each other. Disaccharides includemaltose [glucose-glucose], lactose [galactose-glucose] and sucrose[fructose-glucose].

The term “polysaccharide” includes multiple monosaccharides unitscovalently bound to each other. Polysaccharides include starch,hyaluronic acid, amylose, amylopectin, dextran, cyclodextrin andglycogen.

The term “aminosaccharide” refers to a carbohydrate molecule where oneor more hydroxy groups are replaced by an amino group. This includes themonosaccharides glucosamine and muramic acid and the polysaccharidechitin. The amino groups may be acetylated to includeN-acetyl-D-glucosamine and N-acetyl-D-muramic acid.

The term “deoxysaccharide” refers to a carbohydrate molecule where oneor more hydroxy groups are replaced by hydrogen. These include, forexample, L-rhamnose (6-deoxy-L-mannose), L-fucose (6-deoxy-L-galactose)and D-fucose (rhodeose).

The term “treatment” refers to any treatment of a pathologic conditionin a mammal, particularly a human, and includes: (i) preventing thepathologic condition from occurring in a subject which may bepredisposed to the condition but has not yet been diagnosed with thecondition and, accordingly, the treatment constitutes prophylactictreatment for the disease condition; (ii) inhibiting the pathologiccondition, i.e., arresting its development; (iii) relieving thepathologic condition, i.e., causing regression of the pathologiccondition; or (iv) relieving the conditions mediated by the pathologiccondition.

The term “therapeutically effective amount” refers to that amount of acompound of the invention that is sufficient to effect treatment, asdefined above, when administered to a mammal in need of such treatment.The therapeutically effective amount will vary depending upon thesubject and disease condition being treated, the weight and age of thesubject, the severity of the disease condition, the manner ofadministration and the like, which can readily be determined by one ofordinary skill in the art.

The term “pharmaceutically acceptable salts” includes, but is notlimited to, salts well known to those skilled in the art, for example,mono-salts (e.g. alkali metal and ammonium salts) and poly salts (e.g.di- or tri-salts,) of the compounds of the invention. Pharmaceuticallyacceptable salts of compounds of formula I are where, for example, anexchangeable group, such as hydrogen in —OH or —NH— is replaced with apharmaceutically acceptable cation (e.g. a sodium, potassium, orammonium ion) and can be conveniently be prepared from a correspondingcompound of formula I by, for example, reaction with a suitable base. Incases where compounds are sufficiently basic or acidic to form stablenontoxic acid or base salts, administration of the compounds as saltsmay be appropriate. Examples of pharmaceutically acceptable salts areorganic acid addition salts formed with acids that form a physiologicalacceptable anion, for example, tosylate, methanesulfonate, acetate,citrate, malonate, tartarate, succinate, benzoate, ascorbate,α-ketoglutarate, and α-glycerophosphate. Suitable inorganic salts mayalso be formed, including hydrochloride, sulfate, nitrate, bicarbonate,and carbonate salts. Pharmaceutically acceptable salts may be obtainedusing standard procedures well known in the art, for example, byreacting a sufficiently basic compound such as an amine with a suitableacid affording a physiologically acceptable anion. Alkali metal (forexample, sodium, potassium or lithium) or alkaline earth metal (forexample, calcium) salts of carboxylic acids can also be made.

The term “disease,” “disorder” or “condition” as used herein, means anydisease or other deleterious condition or disease in which therapeuticadministration of a diuretic drug, or pharmaceutical composition, isknown to play a role in treatment thereof. Such diseases or conditionsinclude, without limitation, hypertension, edema, acute renal failure,congestive heart failure, chronic renal failure, ascites, intra-ocularpressure or nephrotic syndrome and complications due to or exacerbatedby those conditions.

The term “diuretic” as used herein, means a drug or other substancetending to promote the formation and excretion of urine.

The term “hypertension” as used herein, refers to a disordercharacterized by elevated blood pressure.

“Antibody” refers to a member of a family of glycosylated proteinscalled immunoglobulins, which can specifically combine with an antigen.

“Antigen” refers to a compound which will give rise to antibodyformation.

“Antigenic determinant” or “antigenic determinant site” refers to theactual site of antibody recognition of the antigen. The term is usedinterchangeably with “epitope”.

“Carrier” refers to a high molecular weight (macromolecular) polymericmaterial, usually a protein, to which an antigen or hapten can be boundor conjugated so as to facilitate antibody formation. Carriers canincorporate labels in their structure, if desired.

“Conjugate” refers to an antigen or hapten chemically bonded to acarrier; a conjugate can contain other groups, as well.

“ELISA” refers to an enzyme-linked immunosorbent assay which employs anantibody or antigen bound to a solid phase and an enzyme-antigen orenzyme-antibody conjugate to detect and quantify the amount of antigenor antibody present in a sample. A description of the ELISA technique isfound in Chapter 22 of the 4th Edition of Basic and Clinical Immunologyby D. P. Sites et al, published by Lange Medical Publications of LosAltos, Calif., in 1982, which is incorporated herein by reference.

“EMIT” refers to an enzyme-multiplied immunoassay technique which uses(1) an enzyme-labeled hapten, (2) specific antibody to the hapten, (3)pretreatment reagent, (4) buffered-enzyme substrate, and (5) standardsto detect the amount of an unknown in a sample. A description of theEMIT technique is found in Enzyme Immunoassay, edited by E. T. Maggio,published in 1980 by CRC Press, Inc., Boca Raton, Fla., particularly onpp. 141-150, 234-5, and 242-3. These materials are incorporated byreference.

“Epitope” refers to that portion of a molecule which is specificallyrecognized by an antibody. It is also referred to as a determinant.

“Fluoroimmunoassay” refers to an antibody-based assay in which thespecies to be measured binds to, displaces or competes for binding witha material labelled with a fluorescent species in an antibody-ligandcomplex. In some embodiments of this assay, the complex is separated andthe presence or absence of fluorescent species gives a measure of theamount of measured species. In other embodiments, the complex hasdifferent fluorescent properties than the uncomplexed fluorescentspecies so that the formation of the complex can be detected withoutseparation of the complex. A description of fluoroimmunoassay techniquesis found in “A Review of Fluoroimmunoassay and ImmunofluorometricAssay”, D. S. Smith et al. (1981) Ann. Clin. Biochem. (1981) 18:253-274which is incorporated herein by reference.

“Hapten” refers to a compound, usually of low molecular weight, whichwhen bound to a larger molecule can give rise to antibody formation.

“Label” refers to a detectable group in a molecule. Among the commonlabels are radioactive species useful in radioimmunoassays, fluorescentspecies useful in fluoroimmunoassays, and enzymatic species useful inthe ELISA and EMIT methods and the like.

“Ligand” refers to any molecule which has an antibody combining site andcan bind to a receptor.

“Standard” refers to a sample of a specific molecule present in a knownconcentration used to quantitate the same specific molecule in anunknown concentration of a different sample.

It will be apparent to one skilled in the art that certain compounds ofthis invention may exist in tautomeric forms, all such tautomeric formsof the compounds being within the scope of the invention.

Unless otherwise stated, structures depicted herein are also meant toinclude all stereochemical forms of the structure; i.e., the R and Sconfigurations for each asymmetric center. Therefore, singlestereochemical isomers as well as enantiomeric and diastereomericmixtures of the present compounds are within the scope of the invention.Unless otherwise stated, structures depicted herein are also meant toinclude compounds that differ only in the presence of one or moreisotopically enriched atoms. For example, compounds having the presentstructures except for the replacement of hydrogen by a deuterium ortritium, or the replacement of a carbon by a ¹³C- or ¹⁴C-enriched carbonare within the scope of this invention.

One aspect of the present invention relates to pharmaceuticalcompositions comprising compounds of formula I. In one preferredembodiment, the composition comprises compounds of formula I wherein R₁,R₃, R₄, R₆ and R₇ are independently H, halogen or lower alkyl. Inanother, X₁ is absent and R₄ is (═O); or X₁ is a bond and R₄ is hydroxy.In another embodiment, X₁R₄ is —OC(O)CH₃. In another embodiment, R₂ is—C(O)OR where R is preferably H or optionally substituted alkyl wherealkyl may be methyl, ethyl, butyl, octyl or undecyl. In anotherembodiment, R₂ is —C(O)NHR where R is preferably H or optionallysubstituted alkyl, cycloalkyl, heterocycloalkyl, aryl or heteroaryl.

In one embodiment of the invention, X₂ is —O— and R₈ is an optionallysubstituted saccharide, preferably a monosaccharide selected from analdohexopyranose, aldopentopyranose, aldopentofuranose or ketose. Inother embodiments, R₈ is D-galactose, D-mannose, D-ribose, D-fucose orL-rhamnose. In a preferred embodiment, R₈ is D-glucose. In one specificembodiment, the compound of formula I is xanthurenic acid8-O-β-D-glucoside.

In another embodiment, X₂ is —O— and R₈ is —CH₂CO₂R or —CH₂C(O)NHR whereR is preferably H or optionally substituted alkyl, cycloalkyl,heterocycloalkyl, aryl or heteroaryl.

According to another embodiment of the invention, the pharmaceuticalcomposition comprises a compound of formula I where X₂R₈ is an acyl,phosphate, phosphonic acid, alkyl phosphonate or a sulfate group. In onespecific embodiment, the compound is xanthurenic acid 8-O-sulfate.

The invention further provides a pharmaceutical composition comprising atherapeutically effective amount of a compound represented by formula Iin combination one or more additional diuretic compounds orcardiovascular agents; and a pharmaceutically acceptable carrier.

The pharmaceutical compositions described herein are useful fortreatment or prevention of hypertension, edema, acute renal failure,congestive heart failure, chronic renal failure, ascites, intra-ocularpressure or nephrotic syndrome and complications due to or exacerbatedby those conditions.

Depending upon the particular condition to be treated or prevented,additional therapeutic agents, which are normally administered to treator prevent that condition, may be administered together with thecompounds of this invention. For example, in the treatment ofhypertension, one or more additional diuretic compounds orcardiovascular agents may be combined with the compounds of thisinvention to treat hypertension. The additional diuretic agent isselected from the group consisting of a loop diuretic, thiazidediuretic, potassium-sparing diuretic, carbonic anhydrase inhibitor andosmotic diuretic. The cardiovascular agent is selected from the groupconsisting of an angiotensin converting enzyme inhibitor, angiotensin IIreceptor antagonist, beta-adrenergic blocker, calcium channel blocker,cholesterol altering drug, triglyceride lowering agent, c-reactiveprotein lowering agent, homocysteine lowering agent, aspirin and itsderivatives, ionotropic agent, antiarrhythmic agent and blood thinner(anticoagulant). These agents include, without limitation, furosemide,bumetanide, torsemide, ethacrynic acid, chlorothiazide,hydrochlorothiazide, spironolactone, amiloride, triamterene,acetazolamide, methazolamide, dichlorphenamide, hydroflumethiazide,methyclothiazide, indapamide, metolazone, polythiazide, chlorthalidone,dorzolamide, brinzolamide, glycerol, mannose, urea, lisinopril,moexipril, enalapril, irbesartan, valsartan, losartan, nadolol,propranolol, atenolol, timolol and bisoprolol.

The compounds of formula I can be formulated as pharmaceuticalcompositions and administered to a mammalian host, such as a humanpatient, in a variety of forms adapted to a selected route ofadministration, i.e., by oral, parenteral, intravenous, intramuscular,topical, or subcutaneous routes. Thus, the present compounds may besystemically administered, e.g., orally, in combination with apharmaceutically acceptable vehicle such as an inert diluent or anassimilable edible carrier. They may be enclosed in hard or soft shellgelatin capsules, may be compressed into tablets, or may be incorporateddirectly with the food of the patient's diet. For oral therapeuticadministration, the active compound may be combined with one or moreexcipients and used in the form of ingestible tablets, buccal tablets,troches, capsules, elixirs, suspensions, syrups, wafers, and the like.Such compositions and preparations should contain at least 0.1% ofactive compound. The percentage of the compositions and preparationsmay, of course, be varied and may conveniently be between about 2 toabout 60% of the weight of a given unit dosage form. The amount ofactive compound in such therapeutically useful compositions is such thatan effective dosage level will be obtained.

The tablets, troches, pills, capsules, and the like may also contain thefollowing: binders such as gum tragacanth, acacia, corn starch orgelatin; excipients such as dicalcium phosphate; a disintegrating agentsuch as corn starch, potato starch, alginic acid and the like; alubricant such as magnesium stearate; and a sweetening agent such assucrose, fructose, lactose or aspartame or a flavoring agent such aspeppermint, oil of wintergreen, or cherry flavoring may be added. Whenthe unit dosage form is a capsule, it may contain, in addition tomaterials of the above type, a liquid carrier, such as a vegetable oilor a polyethylene glycol. Various other materials may be present ascoatings or to otherwise modify the physical form of the solid unitdosage form. For instance, tablets, pills, or capsules may be coatedwith gelatin, wax, shellac or sugar and the like. A syrup or elixir maycontain the active compound, sucrose or fructose as a sweetening agent,methyl and propylparabens as preservatives, a dye and flavoring such ascherry or orange flavor. Of course, any material used in preparing anyunit dosage form should be pharmaceutically acceptable and substantiallynon-toxic in the amounts employed. In addition, the active compound maybe incorporated into sustained-release preparations and devices.

The active compound may also be administered intravenously orintraperitoneally by infusion or injection. Solutions of the activecompound or its salts can be prepared in water, optionally mixed with anontoxic surfactant. Dispersions can also be prepared in glycerol,liquid polyethylene glycols, triacetin, and mixtures thereof and inoils. Under ordinary conditions of storage and use, these preparationscontain a preservative to prevent the growth of microorganisms. Thepharmaceutical dosage forms suitable for injection or infusion caninclude sterile aqueous solutions or dispersions or sterile powderscomprising the active ingredient that are adapted for the extemporaneouspreparation of sterile injectable or infusible solutions or dispersions,optionally encapsulated in liposomes. In all cases, the ultimate dosageform should be sterile, fluid and stable under the conditions ofmanufacture and storage. The liquid carrier or vehicle can be a solventor liquid dispersion medium comprising, for example, water, ethanol, apolyol (for example, glycerol, propylene glycol, liquid polyethyleneglycols, and the like), vegetable oils, nontoxic glyceryl esters, andsuitable mixtures thereof. The proper fluidity can be maintained, forexample, by the formation of liposomes, by the maintenance of therequired particle size in the case of dispersions or by the use ofsurfactants. The prevention of the action of microorganisms can bebrought about by various antibacterial and antifungal agents, forexample, parabens, chlorobutanol, phenol, sorbic acid, thimerosal, andthe like. In many cases, it will be preferable to include isotonicagents, for example, sugars, buffers or sodium chloride. Prolongedabsorption of the injectable compositions can be brought about by theuse in the compositions of agents delaying absorption, for example,aluminum monostearate and gelatin.

Sterile injectable solutions are prepared by incorporating the activecompound in the required amount in the appropriate solvent with variousof the other ingredients enumerated above, as required, followed byfilter sterilization. In the case of sterile powders for the preparationof sterile injectable solutions, the preferred methods of preparationare vacuum drying and the freeze-drying techniques, which yield a powderof the active ingredient plus any additional desired ingredient presentin the previously sterile-filtered solutions. For topicaladministration, the present compounds may be applied in pure form, i.e.,when they are liquids. However, it will generally be desirable toadminister them to the skin as compositions or formulations, incombination with a dermatologically acceptable carrier, which may be asolid or a liquid.

Useful solid carriers include finely divided solids such as talc, clay,microcrystalline cellulose, silica, alumina and the like. Useful liquidcarriers include water, alcohols or glycols or water-alcohol/glycolblends, in which the present compounds can be dissolved or dispersed ateffective levels, optionally with the aid of non-toxic surfactants.Adjuvants such as fragrances and additional antimicrobial agents can beadded to optimize the properties for a given use. The resultant liquidcompositions can be applied from absorbent pads, used to impregnatebandages and other dressings, or sprayed onto the affected area usingpump-type or aerosol sprayers.

Thickeners such as synthetic polymers, fatty acids, fatty acid salts andesters, fatty alcohols, modified celluloses or modified mineralmaterials can also be employed with liquid carriers to form spreadablepastes, gels, ointments, soaps, and the like, for application directlyto the skin of the user.

Examples of useful dermatological compositions which can be used todeliver the compounds of the invention to the skin are disclosed inJacquet et al. (U.S. Pat. No. 4,608,392), Geria (U.S. Pat. No.4,992,478), Smith et al, (U.S. Pat. No. 4,559,157) and Wortzman (U.S.Pat. No. 4,820,508).

The present compositions may also be prepared in suitable forms forabsorption through the mucous membranes of the nose and throat orbronchial tissues and may conveniently take the form of powder or liquidsprays or inhalants, lozenges, throat paints, etc. For medication of theeyes or ears, the preparations may be presented as individual capsules,in liquid or semi-solid form, or may be used as drops, etc. Topicalapplications may be formulated in hydrophobic or hydrophilic bases asointments, creams, lotions, paints, powders, etc.

For veterinary medicine, the composition may, for example, be formulatedas an intra-mammary preparation in either long acting or quick-releasebases.

Useful dosages of the compounds of the invention can be determined bycomparing their in vitro activity, and in vivo activity in animalmodels. Methods for the extrapolation of effective dosages in mice, andother animals, to humans are known to the art; for example, see U.S.Pat. No. 4,938,949.

Generally, the concentration of the compound(s) of the invention in aliquid composition, such as a lotion, will be from about 0.1-25 wt-%,preferably from about 0.5-10 wt-%. The concentration in a semi-solid orsolid composition such as a gel or a powder will be about 0.1-5 wt-%,preferably about 0.5-2.5 wt-%.

The compositions per unit dosage, whether liquid or solid may containfrom 0.1% to 99% of active material (compound I or salts thereof), thepreferred range being from about 10-60%. The composition will generallycontain from about 15 mg to about 1,500 mg by weight of activeingredient based upon the total weight of the composition; however, ingeneral, it is preferable to employ a dosage amount in the range of fromabout 250 mg to 1,000 mg. In parenteral administration the unit dosageis usually the pure compound in a slightly acidified sterile watersolution or in the form of a soluble powder intended for solution.Single dosages for injection, infusion or ingestion may be administered,i.e., 1-3 times daily, to yield levels of about 0.5-50 mg/kg, foradults.

Production of Antibodies

The present disclosure further includes methods for the production ofantibodies capable of specifically recognizing xanthurenicacid-8-O-β-D-glucoside. Such antibodies may include, but are not limitedto, polyclonal antibodies, monoclonal antibodies (mAbs), humanized orchimeric antibodies, single chain antibodies, Fab fragments, F(ab′)₂fragments, fragments produced by a Fab expression library,anti-idiotypic (anti-Id) antibodies, and epitope-binding fragments ofany of the above. Such antibodies may be used, for example, in thedetection of xanthurenic acid-8-O-β-D-glucoside in a biological sample,or, alternatively, as a method for the inhibition of abnormalxanthurenic acid-8-O-β-D-glucoside activity. Thus, such antibodies maybe utilized as part of disease treatment methods, and/or may be used aspart of diagnostic techniques whereby patients may be tested forabnormal levels of xanthurenic acid-8-O-β-D-glucoside.

For the production of antibodies, conjugates of xanthurenicacid-8-O-β-D-glucoside with, for example, a carrier protein such as KLHor ovalbumin, may be generated by activation of the xanthurenicacid-8-O-β-D-glucoside carboxyl group with, for example, a water solublecarbodiimide, such as EDC, to form a xanthurenic acid-8-O-β-D-glucosidebioconjugate immunogen. Various host animals may be immunized byinjection with the xanthurenic acid-8-O-β-D-glucoside bioconjugateimmunogen in, for example, an adjuvanted protocol. Such host animalsinclude rabbits, mice, rats, goats and chickens, and the like. Variousadjuvants may be used to increase the immunological response, dependingon the host species, including but not limited to Freund's (complete andincomplete), mineral gels such as aluminum hydroxide, surface activesubstances such as lysolecithin, pluronic polyols, polyanions, peptides,oil emulsions, keyhole limpet hemocyanin, dinitrophenol, and potentiallyuseful human adjuvants such as BCG (bacille Calmette-Guerin) andCorynebacterium parvum.

Polyclonal antibodies are heterogeneous populations of antibodymolecules derived from the sera of animals immunized with an antigen,such as xanthurenic acid-8-O-β-D-glucoside bioconjugate immunogen. Forthe production of polyclonal antibodies, host animals such as thosedescribed above, may be immunized by injection with xanthurenicacid-8-O-β-D-glucoside bioconjugate immunogen supplemented withadjuvants as also described above.

Methods for generating polyclonal antibodies to antigens using hostanimals are known generally to the art. In a typical preparation, one ormore of the xanthurenic acid-8-O-β-D-glucoside bioconjugate immunogensis introduced into a mammalian or avian host. Suitable hosts include,for example, monkeys, cattle, rabbits, rats, mice, and the like. This isusually accomplished by subcutaneous injection as a solution in salinewhich has been emulsified with, for example, complete Freund's adjuvant.Animal antibody titers may be followed by ELISA. After several weeks, aboost of xanthurenic acid-8-O-β-D-glucoside bioconjugate immunogen in,for example, Freund's incomplete adjuvant, may serve to increase theantibody titer. The antibodies are collected by bleeding the animalafter about a month. The whole blood is allowed to clot at 25.degree. C.for several hours. Aqueous ammonium sulfate solution is added to achieve40% by weight of aqueous solution, and the IgG fraction precipitates.The precipitate is collected by centrifugation and resuspended in salineor buffer solution to the desired concentration.

The purified antibody fraction may be further modified for use indiagnostic assay systems. Such modification may encompass linkage withenzymes such as lipozyme, lactoperoxidase, alkaline phosphatase andothers for use in ELISA assays. The antibody may be modified withfluorescent moieties. Optimally, this fluorescence may be quenched orenhanced upon binding of the antibody and antigen. These techniques forassaying the extent of the antibody-antigen interaction are known in theart. The xanthurenic acid-8-O-β-D-glucoside, xanthurenicacid-8-O-β-D-glucoside conjugates and antibodies of this disclosure arealso useful in the detection and diagnosis of various sodium imbalancedisorders, particularly in providing high purity materials useful forcalibration solutions for assay techniques, such as ELISA or EMIT.

Monoclonal antibodies, which are homogeneous populations of antibodiesto a particular antigen, may be obtained by any technique that providesfor the production of antibody molecules by continuous cell lines inculture. These include, but are not limited to the hybridoma techniqueof Köhler and Milstein, Nature, 256:495-7 (1975); and U.S. Pat. No.4,376,110), the human B-cell hybridoma technique (Kosbor et al.,Immunology Today, 4:72 (1983); Cote et al., Proc. Natl. Acad. Sci. USA,80:2026-30 (1983)), and the EBV-hybridoma technique (Cole et al., inMonoclonal Antibodies And Cancer Therapy, Alan R. Liss, Inc., New York,pp. 77-96 (1985)). Such antibodies may be of any immunoglobulin classincluding IgG, IgM, IgE, IgA, IgD and any subclass thereof. Thehybridoma producing the mAb of this disclosure may be cultivated invitro or in vivo. Production of high titers of mAbs in vivo makes thisthe presently preferred method of production.

In addition, techniques developed for the production of “chimericantibodies” (Morrison et al., Proc. Natl. Acad. Sci., 81:6851-6855(1984); Takeda et al., Nature, 314:452-54 (1985)) by splicing the genesfrom a mouse antibody molecule of appropriate antigen specificitytogether with genes from a human antibody molecule of appropriatebiological activity can be used. A chimeric antibody is a molecule inwhich different portions are derived from different animal species, suchas those having a variable region derived from a murine mAb and a humanimmunoglobulin constant region.

Alternatively, techniques described for the production of single chainantibodies (U.S. Pat. No. 4,946,778; Bird, Science 242:423-26 (1988);Huston et al., Proc. Natl. Acad. Sci. USA, 85:5879-83 (1988); and Wardet al., Nature, 334:544-46 (1989)) can be adapted to produce gene-singlechain antibodies. Single chain antibodies are typically formed bylinking the heavy and light chain fragments of the Fv region via anamino acid bridge, resulting in a single chain polypeptide.

Antibody fragments that recognize specific epitopes may be generated byknown techniques. For example, such fragments include but are notlimited to: the F(ab′)₂ fragments that can be produced by pepsindigestion of the antibody molecule and the Fab fragments that can begenerated by reducing the disulfide bridges of the F(ab′)₂ fragments.Alternatively, Fab expression libraries may be constructed (Huse et al.,Science, 246:1275-81 (1989)) to allow rapid and easy identification ofmonoclonal Fab fragments with the desired specificity.

The enzymes for use in the diagnostic reagents, standards or kits canvary widely, depending on the ease of conjugation, turnover rate, andthe physiological fluid in which the unknown (analyte) is to bemeasured. Representative enzymes of choice include hydrolysases,nucleases, amidases, esterases and the like which are found in U.S. Pat.No. 3,817,837, which is incorporated herein by reference.

The methods and apparatus for labeling an antibody as described hereinfor use in a diagnostic reagent, standard or kit is found in U.S. Pat.No. 4,366,241, which is incorporated herein by reference.

Diagnostics

The present invention further includes the quantitation of xanthurenicacid-8-O-β-D-glucoside in human fluids (whole blood, urine, csf, serum,plasma, ocular, feces, sweat) which may be used to correlate to adisorder of sodium imbalance. Such disorders may include hypertension(low renin, low angiotensin), congestive heart failure (edema),nephrotic syndrome, cirrosis of the liver, premenstrual edema, cyclicaledema, and cardiogenic shock. Other clinical conditions in whichxanthurenic acid-8-O-β-D-glucoside quantitation may prove useful includepost-operative settings, and battlefield settings, where the patient isgiven too much fluid; and potassium-sparing in conjunction withfurosemide administration. Xanthurenic acid-8-O-β-D-glucosidequantitation may also be useful in “Escape Syndrome” where a tumorinappropriately increases, affecting aldosterone; then sodium excretiondecreases causing increase of fluid retention by two liters in thecardiovascular system. At this point, “escape” occurs by causing fluidand sodium loss and thus maintaining an overloaded state of two liters.It is proposed that the overloaded fluid state causes an increase inxanthurenic acid-8-O-β-D-glucoside, which in turn causes “escape” bystimulating sodium excretion and concomitant fluid loss.

A variety of methods may be employed to diagnose disease conditionsassociated with an excess or a deficiency of xanthurenicacid-8-O-β-D-glucoside.

The methods described herein may be performed, for example, by utilizingpre-packaged diagnostic kits comprising at least one specific antibodyreagent described herein, which may be conveniently used, e.g., inclinical, settings, to diagnose patients exhibiting disease symptoms orat risk for developing disease.

Any human biological sample or tissue may be utilized in the diagnosticsdescribed below. For example, whole blood, urine, saliva, cerebralspinal fluid, serum, plasma, ocular, feces or sweat may be utilized.

Diagnostic methods for the detection of xanthurenicacid-8-O-β-D-glucoside in biological samples may involve, for example,immunoassays such as heterogeneous enzyme immunoassays which includesolid phase enzyme-linked immunosorbent assays (ELISA); and solutionphase homogeneous enzyme immunoassays which include enzyme-multipliedimmunoassay technique (EMIT). Xanthurenic acid-8-O-β-D-glucoside may bemeasured by high pressure liquid chromatography (HPLC), capillaryelectrophoresis (CE), or capillary electrophoresis-mass spectrometry(CE-MS) with optional pretreatment of, for example, a urine sample bysolid phase extraction. Further, surface plasmon resonance (SPR)techniques may be developed in which a chip-based optical biosensorsystem is used to investigate the functional nature of xanthurenicacid-8-O-β-D-glucoside binding to target membrane molecules in which thesource of xanthurenic acid-8-O-β-D-glucoside is from an impure mixture,such as serum, urine, and cell culture media. SPR techniques will beuseful in finding and characterizing membrane receptors for xanthurenicacid-8-O-β-D-glucoside in different cells types.

Immunoassays for xanthurenic acid-8-O-β-D-glucoside typically compriseincubating a biological sample, such as a biological fluid, a tissueextract, freshly harvested cells, or cells that have been incubated intissue culture, in the presence of a detectably labeled antibody capableof identifying xanthurenic acid-8-O-β-D-glucoside, and detecting thebound antibody by any of a number of techniques well known in the art.

The biological sample may be brought in contact with and immobilizedonto a solid phase support or carrier such as nitrocellulose, or othersolid support that is capable of immobilizing cells, cell particles orsoluble proteins. The support may then be washed with suitable buffersfollowed by treatment with the detectably labeled gene-specificantibody. The solid phase support may then be washed with the buffer asecond time to remove unbound antibody. The amount of bound label onsolid support may then be detected by conventional means.

The terms “solid phase support or carrier” are intended to encompass anysupport capable of binding an antigen or an antibody. Well-knownsupports or carriers include glass, polystyrene, polypropylene,polyethylene, dextran, nylon, amylases, natural and modified celluloses,polyacrylamides, gabbros, and magnetite. The nature of the carrier canbe either soluble to some extent or insoluble for the purposes of thepresent disclosure. The support material may have virtually any possiblestructural configuration so long as the coupled molecule is capable ofbinding to an antigen or antibody. Thus, the support configuration maybe spherical, as in a bead, or cylindrical, as in the inside surface ofa test tube, or the external surface of a rod. Alternatively, thesurface may be flat such as a sheet, test strip, etc. Preferred supportsinclude polystyrene beads. Those skilled in the art will know many othersuitable carriers for binding antibody or antigen, or will be able toascertain the same by use of routine experimentation.

In practice, microtiter plates are conveniently utilized for manyimmunoassays. The anchored component may be immobilized by non-covalentor covalent attachments. Non-covalent attachment may be accomplishedsimply by coating the solid surface with a solution of a xanthurenicacid-8-O-β-D-glucoside bioconjugate and drying. Alternatively, animmobilized antibody, preferably a monoclonal antibody, specific forxanthurenic acid-8-O-β-D-glucoside may be used to anchor the protein tothe solid surface. The surfaces may be prepared in advance and stored.In order to conduct the assay, the nonimmobilized component is added tothe coated surface containing the anchored component. After the reactionis complete, unreacted components are removed (e.g., by washing) underconditions such that any complexes formed will remain immobilized on thesolid surface. The detection of complexes anchored on the solid surfacecan be accomplished in a number of ways. Where the previouslynonimmobilized component is pre-labeled, the detection of labelimmobilized on the surface indicates that complexes were formed. Wherethe previously nonimmobilized component is not pre-labeled, an indirectlabel can be used to detect complexes anchored on the surface; e.g.,using a labeled antibody specific for the previously nonimmobilizedcomponent (the antibody, in turn, may be directly labeled or indirectlylabeled with a labeled anti-Ig antibody).

For example, competitive inhibition assays are often used to measuresmall analytes, such as xanthurenic acid-8-O-β-D-glucoside, becausecompetitive inhibition assays only require the binding of one antibodyrather than two as is used in standard ELISA formats. Because of theprobability for steric hindrance occurring when two antibodies attemptto bind to a small molecule at the same time, a sandwich assay formatmay not be feasible, therefore a competitive inhibition assay may bepreferable. In a sequential competitive inhibition assay, the sample andconjugated analyte are added in steps like a sandwich assay, while in aclassic competitive inhibition assay, these reagents are incubatedtogether at the same time.

In a sequential competitive inhibition assay format, a monoclonalantibody (MAb) is coated onto a 96-well microtiter plate. When thesample is added, the MAb captures free analyte out of the sample. In thenext step, a known amount of analyte labeled with either biotin or HRPis added. The labeled analyte will then also attempt to bind to the MAbadsorbed onto the plate, however, the labeled analyte is inhibited frombinding to the MAb by the presence of previously bound analyte from thesample. This means that the labeled analyte will not be bound by themonoclonal on the plate if the monoclonal has already bound unlabeledanalyte from the sample. The amount of unlabeled analyte in the sampleis inversely proportional to the signal generated by the labeledanalyte. The lower the signal, the more unlabeled analyte there is inthe sample. A standard curve can be constructed using serial dilutionsof an unlabeled analyte standard. Subsequent sample values can then beread off the standard curve as is done in the sandwich ELISA formats.

The classic competitive inhibition assay format requires thesimultaneous addition of labeled (conjugated analyte) and unlabeledanalyte (from the sample). Both labeled and unlabeled analyte thencompete simultaneously for the binding site on the monoclonal captureantibody on the plate. Like the sequential competitive inhibitionformat, the colored signal is inversely proportional to theconcentration of unlabeled target analyte in the sample.

Detection of labeled analyte may be made by using a peroxidase substratesuch as TMB, which can be read on a microtiter plate reader. Forexample, with a standard curve (1 blank and 7 standards) and 3 controls,a 96-well microtiter plate format can test 21 samples in triplicate and37 samples in duplicate.

As another example, antibodies, or fragments of antibodies useful in thepresent disclosure may be used to quantitatively or qualitatively detectthe presence of xanthurenic acid-8-O-β-D-glucoside. This can beaccomplished, for example, by immunofluorescence techniques employing afluorescently labeled antibody (see below) coupled with lightmicroscopic, flow cytometric, or fluorimetric detection.

The antibodies (or fragments thereof) useful in the present disclosuremay, additionally, be employed histologically, as in immunofluorescenceor immunoelectron microscopy, for in situ detection of xanthurenicacid-8-O-β-D-glucoside. In situ detection may be accomplished byremoving a histological specimen from a patient, and applying thereto alabeled antibody of the present disclosure. The antibody (or fragment)is preferably applied by overlaying the labeled antibody (or fragment)onto a biological sample. Through the use of such a procedure, it ispossible to determine not only the presence of the xanthurenicacid-8-O-β-D-glucoside, but also their distribution in the examinedtissue. Using the present disclosure, those of ordinary skill willreadily perceive that any of a wide variety of histological methods(such as staining procedures) can be modified in order to achieve suchin situ detection.

Those skilled in the art will be able to determine operative and optimalassay conditions for each determination by employing routineexperimentation.

One of the ways in which the gene peptide-specific antibody can bedetectably labeled is by linking the same to an enzyme and using it inan enzyme immunoassay (EIA) (Voller, Ric Clin Lab, 8:289-98 (1978) [“TheEnzyme Linked Immunosorbent Assay (ELISA)”, Diagnostic Horizons 2:1-7,1978, Microbiological Associates Quarterly Publication, Walkersville,Md.]; Voller et al., J. Clin. Pathol., 31; 507-20 (1978); Butler, Meth.Enzymol., 73:482-523 (1981); Maggio (ed.), Enzyme Immunoassay, CRCPress, Boca Raton, Fla. (1980); Ishikawa et al., (eds.) EnzymeImmunoassay, Igaku-Shoin, Tokyo (1981)). The enzyme that is bound to theantibody will react with an appropriate substrate, preferably achromogenic substrate, in such a manner as to produce a chemical moietythat can be detected, for example, by spectrophotometric, fluorimetricor by visual means. Enzymes that can be used to detectably label theantibody include, but are not limited to, malate dehydrogenase,staphylococcal nuclease, delta-5-steroid isomerase, yeast alcoholdehydrogenase, alpha-glycerophosphate, dehydrogenase, triose phosphateisomerase, horseradish peroxidase, alkaline phosphatase, asparaginase,glucose oxidase, beta-galactosidase, ribonuclease, urease, catalase,glucose-6-phosphate dehydrogenase, glucoamylase andacetylcholinesterase. The detection can be accomplished by colorimetricmethods that employ a chromogenic substrate for the enzyme. Detectionmay also be accomplished by visual comparison of the extent of enzymaticreaction of a substrate in comparison with similarly prepared standards.

Detection may also be accomplished using any of a variety of otherimmunoassays. For example, by radioactively labeling the antibodies orantibody fragments, it is possible to detect xanthurenicacid-8-O-β-D-glucoside through the use of a radioimmunoassay (RIA) (see,e.g., Weintraub, B., Principles of Radioimmunoassays, Seventh TrainingCourse on Radioligand Assay Techniques, The Endocrine Society, March,1986). The radioactive isotope can be detected by such means as the useof a gamma counter or a scintillation counter or by autoradiography.

It is also possible to label the antibody with a fluorescent compound.When the fluorescently labeled antibody is exposed to light of theproper wave length, its presence can then be detected due tofluorescence. Among the most commonly used fluorescent labelingcompounds are fluorescein isothiocyanate, rhodamine, phycoerythrin,phycocyanin, allophycocyanin, o-phthaldehyde and fluorescamine.

The antibody can also be detectably labeled using fluorescence emittingmetals such as ¹⁵²Eu, or others of the lanthanide series. These metalscan be attached to the antibody using such metal chelating groups asdiethylenetriaminepentacetic acid (DTPA) or ethylenediamine-tetraaceticacid (EDTA).

The antibody also can be detectably labeled by coupling it to achemiluminescent compound. The presence of the chemiluminescent-taggedantibody is then determined by detecting the presence of luminescencethat arises during the course of a chemical reaction. Examples ofparticularly useful chemiluminescent labeling compounds are luminol,isoluminol, theromatic acridinium ester, imidazole, acridinium salt andoxalate ester.

Likewise, a bioluminescent compound may be used to label the antibody ofthe present disclosure. Bioluminescence is a type of chemiluminescencefound in biological systems in which a catalytic protein increases theefficiency of the chemiluminescent reaction. The presence of abioluminescent protein is determined by detecting the presence ofluminescence. Important bioluminescent compounds for purposes oflabeling are luciferin, luciferase and aequorin.

Throughout this application, various publications, patents and publishedpatent applications are referred to by an identifying citation. Thedisclosures of these publications, patents and published patentspecifications referenced in this application are hereby incorporated byreference into the present disclosure to more fully describe the stateof the art to which this disclosure pertains.

Enzyme-multiplied immunoassay techniques (EMIT) may be employed due tothe small size of xanthurenic acid-8-O-β-D-glucoside. Various EMITmethods could be used in both qualitative and quantitative assays by,for example, the methods described by Dias, et al. (see Dias et al.,“The EMIT Cyclosporine Assay: development of application protocols forthe Boehringer Mannheim Hitachi 911 and 917 analyzers” Clin. Biochem.1997 March; 30(2):155-62). Advantages of EMIT in the clinical settinginclude (1) minimal or no sample preparation, (2) small sample size, (3)excellent correlation with other methods such as HPLC and RIA, (4) rapidtime since there is no need for separation of free and bound enzymelabels (less than one minute), ease of adaptation to most generalchemistry analyzers.

Surface plasmon resonance (SPR) may also be employed to detectxanthurenic acid-8-O-β-D-glucoside as a solution phase interactant toimmobilized xanthurenic acid-8-O-β-D-glucoside specific antibody. Thetechniques of McDonnell and of Rich et al. may be employed for the SPRmethods development (McDonnell, J. M., “Surface plasmon resonance:towards an understanding of the mechanisms of biological molecularrecognition. Current Opinion in Chemical Biology, 2001. 5(5): p.572-577; Rich, R. L., et al., “High-resolution and high-throughputprotocols for measuring drug/human serum albumin interactions usingBIACORE” Analytical Biochemistry, 2001. 296(2): p. 197-207). Variousflow-through cells may be constructed and placed in-line withcommercially available SPR biosensing instruments, such as those withtrademark Biocore. In general, the specific antibody may be immobilizedon an SPR-active gold-coated glass slide which forms one wall of aflow-cell; and the analyte xanthurenic acid-8-O-β-D-glucoside in anaqueous buffer solution is injected to flow across the flow-cell. Whenlight (visible or near infrared) is shined through the glass slide andonto the gold surface at angles and wavelengths near the so-called“surface plasmon resonance” condition, the optical reflectivity of thegold changes very sensitively with the presence of biomolecules on thegold surface or in a thin coating on the gold. The extent of bindingbetween the solution-phase interactant and the immobilized antibody iseasily observed and quantified by monitoring this reflectivity change.

High pressure liquid chromatography (HPLC) may be employed to detectxanthurenic acid-8-O-b-D-glucoside in urine. For example, urine samplesolid phase extraction on a C₁₈ cartridge and subsequent passage over acation-exchange resin column may be employed. Sample detection may bevia UV, fluorescence, or light scattering techniques. (see, for example,Marsilio et al., Clinical Chemistry. 1998; 44:1685-1691.) Capillaryelectrophoresis (CE), or capillary electrophoresis-mass spectrometry(CE-MS) with optional pretreatment of urine sample by solid phaseextraction may also be employed to quantitate xanthurenicacid-8-O-β-D-glucoside in biological samples. (He et al., J Chromatogr BBiomed Sci Appl. 1999 Apr. 30; 727(1-2):43-52; Theodoridis et al., JChromatogr B Biomed Sci Appl. 2000 Aug. 4; 745(1):49-82.)

The invention will now be described in greater detail by reference tothe following non-limiting examples.

EXAMPLES Example 1 Synthesis of Xanthurenic Acid 8-O-β-D-glucoside

Step 1: Synthesis of xanthurenic acid 2,3,4,6-tetra-O-acetyl8-O-β-D-glucoside. (See, for example, Real, et al., J. Biol. Chem.,1990, 265(13), 7407-7412)

Xanthurenic acid was obtained commercially from Aldrich, Milwaukee, Wis.Xanthurenic acid (930 mg, 4.53 mmol) in aqueous 1M NaOH (10 mL) wascooled to 10° C. 2,3,4,6-tetra-O-acetyl 8-α-D-glucopyranosylbromide(2.03 g, 4.94 mmol) in acetone (16 mL) was added dropwise over 10minutes. The solution was allowed to warm to room temperature over 4hours. Additional aqueous 1M NaOH (3 mL) was added slowly over 30minutes and solution stirred 30 minutes. The mixture was extracted withwater and diethyl ether. The aqueous portion was acidified to pH 3.5 andfurther extracted with 1:1 tetrahydrofuran/ethylacetate. The combinedorganic layers were washed with saturated aqueous NaCl and dried overmagnesium sulfate. Following filtration, the crude xanthurenic acidtetra-O-acetyl 8-β-D-glucoside intermediate was concentrated in vacuo togive approximately 1 gram of a crude residue. The residue was trituratedwith 4:1 dimethylsulfoxide/water (28 mL), filtered and dried to return215 mg of xanthurenic acid tetra-O-acetyl 8-β-D-glucoside as anoff-white solid intermediate. The mother liquor was further purified byhigh-pressure liquid chromatography (HPLC) to recover an additional 60mg of intermediate (C18, water/acetonitrile with 0.2% trifluoroaceticacid; step elution) for a combined 11.5% yield. ¹H NMR (300 MHz,DMSO-d₆) δ 1.97 (s, 3H), 1.99 (s, 3H), 2.00 (s, 3H), 2.06 (s, 3H),4.05-4.30 (m, 3H), 5.07 (d, J=9.6 Hz, 1H), 5.23 (dd, J=9.6, 7.8 Hz, 1H),5.44 (t, J=9.60 Hz, 1H), 5.67 (d, J=7.8 Hz, 1H), 6.65 (s, 1H), 7.37 (t,J=8.1 Hz, 1H), 7.48 (dd, J=7.5, 1.2 Hz, 1H), 7.81 (dd, J=8.1, 1.2 Hz,1H), 9.44 (bs, 1H). ESI-MS m/z 536.44 (M+H⁺).

Step 2: Xanthurenic acid 8-O-β-D-glucoside.

Xanthurenic acid 2,3,4,6-tetra-O-acetyl 8-O-β-D-glucoside from step 1(190 mg, 0.35 mmol) was added to a solution of 95% sodium methoxide (40mg, 0.7 mmol) in methanol (5 mL). The mixture was stirred for one hour.The mixture was adjusted to pH 3.5 with aqueous 1M HCl. The slurry wasdiluted with 20 mL diethyl ether and filtered. The filter cake waswashed with 1:1 methanol/diethyl ether and dried in vacuo to give 118 mgof xanthurenic acid 8-O-β-D-glucoside in an 82% yield. FTIR (neat)3000-3700 (br, s), 3365, 2934, 1626, 1602 cm¹. ¹H NMR (300 MHz, DMSO-d₆)δ 3.10-3.70 (m, 6H and H₂O), 4.87 (d, J=7.5 Hz, 1H), 4.95 (m, 1H), 5.16(m, 1H), 5.33 (m, 1H), 5.81 (m, 1H), 6.47 (s, 1H), 7.21 (t, J=8.0 Hz,1H), 8.07 (d, J=7.2 Hz, 1H), 8.24 (dd, J=8.4, 1.0 Hz, 1H), 8.47 (s, <1H,partial exchange), 10.47 (br s, 1H). ¹³C-NMR (75.4 MHz, DMSO-d₆) δ60.74, 69.62, 73.49, 76.56, 77.66, 103.73, 107.73, 119.65, 122.72,126.79, 132.00, 146.24, 147.05, 162.85, 166.88, 178.33. Electrosprayionization mass spectra (ESI-MS) m/z 368.31 (M+H⁺).

Example 2 Synthesis of Xanthurenic Acid 8-O-sulfate

To a solution of xanthurenic acid (300 mg, 1.46 mmol) in 2.9 mL of 1 NNaOH and 2.1 mL of dH₂O (deionized water) were added sulfurtrioxidetrimethylamine (407 mg, 2.92 mmol) and 5 mL of acetone at roomtemperature. The reactor (20×125 mm tube) was sealed under nitrogen andstirred at 70° C. for 16 hours. The reaction was cooled to roomtemperature and concentrated to dryness under reduced pressure. Theresidue was washed with acetone, acetonitrile, dichloromethane, ethylacetate and then diethyl ether consecutively. The collected solid wasplaced under vacuum overnight. The solid was dissolved in 3 mL dH₂O,loaded to a SEPHADEX SP-C25 gel filtration column (4×11 cm, 40-125μ) andeluted with dH₂O to afford the sodium salt of the title compound (474mg, 1.44 mmol) in a 98.8% yield as a shiny brown powder with mp>250° C.(dec.). ¹H NMR (300 MHz, D₂O) δ 6.67 (br s, 1H), 7.28 (br dd, J=8.1, 7.8Hz, 1H), 7.56 (br d, J=7.8 Hz, 1H), 7.79 (br d, J=8.1 Hz, 1H). ¹³C NMR(75 MHz, D₂O) δ 108.5, 122.1, 124.9 125.6, 126.1, 132.6 140.7, 144.7,166.3, 181.0. IR (solid, cm⁻¹) 2835, 2545, 1687, 1601, 1372, 1372, 1254.

Example 3 Isolation of xanthurenic acid 8-O-sulfate and xanthurenic acid8-O-β-D-glucoside

Urine samples from human uremic patients were collected over 24-hourperiods. The typical collection volume was of 2-3 liters per patient.Individual samples were lyophilized to dryness and reconstituted with100 mL of deionized water. The reconstituted samples (25 mL load volume)were size-fractionated using gel filtration SEPHADEX G-25 columnchromatography with elution by 10 mM ammonium acetate, pH 6.8 at 10° C.and monitored by UV at 285 nm and conductivity. Later eluting (post-saltpeak) 10 mL fractions with UV activity and osmolality <100 mOsm werescreened for biological activity with the frog skin assay of Bricker etal. (Kidney International Vol 44 (1993) November; 44 (5): 937-47).Fractions with activity (10 mL each) were concentrated by lyophilizationand reconstituted with 1 mL deionized water.

Reconstituted Sephadex G-25 fractions with biological activity werefurther fractionated with high performance liquid chromatography (HPLC;1 mL load volume) over an octadecylsilyl (Phenomenex SphereClone ODS2,35° C.) semi-preparative HPLC column at 4 mL/minute with a 0.1 Mpyridium acetate:methanol gradient; 0-40% methanol/11 minutes withcollection of 2 mL fractions. Elution was monitored by fluorescence(excitation 332 nm, emission at 430 nm) and UV (338 nm). Fractions witha retention time (RT) of 12.4 minutes were pooled from multiple runs andconcentrated approximately 10-fold. The fractions were re-applied to theHPLC system above with a 1 mL injection volume run in isocratic modewith 92% 0.1 M/8% methanol at 4 mL/minute. Fluorescence was monitoredwith excitation 332 nm, emission 430 nm. UV was monitored at 338 nm.These maxima are for xanthurenic acid 8-O-β-D-glucoside. Eluate between10-13 minutes was collected in 12 second (0.8 mL) fractions. Fractionseluting between 11.2-11.6 minutes RT contained xanthurenic acid8-O-β-D-glucoside; fractions eluting between 12.0-12.5 minutes containedxanthurenic acid 8-O-sulfate. Fractions containing either thexanthurenic acid 8-O-β-D-glucoside or the xanthurenic acid 8-O-sulfatewere separately pooled and concentrated on a Savant Speed-Vac Plus(SC210A) with medium heat. The pools were resubjected to isocratic HPLCon an analytical scale using a reverse phase C-18 HPLC column:Phenomenex P/NO 00G-4375-E0, SYNERGI 4u Hydro-RP 80A 250×4.6 mm, 4micron. The HPLC purification was run in isocratic mode at 1 mL/minutewith 8% methanol and 0.1% 0.1M pyridium acetate at 35° C. Elution wasmonitored by UV absorbance at 338 nm and fluorescence detection withexcitation 332 nm, emission 430 nm. Fractions containing xanthurenicacid 8-O-β-D-glucoside had RT=10.2-10.6 minutes. Fractions from separatexanthurenic acid 8-O-sulfate runs had RT=11-11.5 minutes. Fractions werepooled and concentrated on a Speed-Vac, with occasional addition ofpyridine to increase pH. The purified xanthurenic acid 8-O-β-D-glucosidewas reapplied to the same analytical column and eluted with 20% methanolin water to eliminate pyridium acetate. Xanthurenic acid8-O-β-D-glucoside formed crystals upon concentration by this technique.For isolated xanthurenic acid 8-O-β-D-glucoside (C₁₆H₁₇NO₉): ESI-MS(m/z) 367.09, 368.094 (M+H) and 229 (M-glucose+Na⁺); ¹H-NMR (500 MHz,D₂O) δ 3.58 (dd, J=9, 9.5 Hz, 1H), 3.65 (dd, J=9, 9.5 Hz, 1H), 3.67 (m,1H), 3.80 (dd, 1H), 3.81 (dd, J=8, 9.5 Hz), 3.95 (dd, 1H), 5.24 (d, J=8Hz, 1H), 6.93 (s, 1H), 7.47 (t, J=8 Hz, 1H), 7.59 (dd, J=8, 2 Hz, 1H),7.90 (dd, J=8, 2 Hz) ppm; ¹³C-NMR (126 MHz, D₂O/CD₃OD) δ 60.8, 69.7,72.9, 75.7, 76.7, 101.2, 108.1, 117.9, 118.2, 124.5, 125.2, 130.6,143.9, 145.5, 165.9, 180.3 ppm. For isolated xanthurenic acid8-O-sulfate (C₁₀H₇NO₇S): ESI-MS (m/z) 284.994, 285.998 (M+H⁺).

Example 4 Natriuretic Response to Synthetic Xanthurenic Acid8-O-β-D-glucoside (2 μg i.v.) in a Normal Sprague Dawley Rat

A female Sprague Dawley rat (250 g) was anesthetized lightly with etherand a tail vein catheter was placed using PE10 tubing. Additionally, aurethra catheter was inserted using KY jelly and 2% lidocaine as alubricant. The rat was restrained in a modified Plexiglas tube so thaturine could be collected in 1.5-mL microcentrifuge tubes. Salineinfusion started at time zero at 0.02 mL/min for the duration of theassay. The same i.v. catheter was used to inject the test compound.Synthetic xanthurenic acid 8-O-β-D-glucoside, 2 μg, was injected at thetime indicated in a 1-mL volume in saline over the course of 10 minutes.The tubes were centrifuged at 14,000 rpm to separate any RBC's from theurine. Na⁺ and K⁺ concentrations in the urine were measured withrespective ion selective electrodes. The Na⁺ and K⁺ excretion rates werecalculated by: (vol of urine/time of collection period)×(ion urineconcentration). Results are shown in FIGS. 1-4. Synthetic xanthurenicacid 8-O-β-D-glucoside at 2 ug i.v. caused a sustained natriureticresponse in a normal rat. Na⁺ excretion was due more to increased Na⁺urine concentration than increased urine volume as shown in FIGS. 3 and4. Given an extracellular volume of 50 mL in a 250-g rat, theconcentration of the test compound was 10⁻⁶ M, a possible minimum dose.In a similar experiment; synthetic, underivatized xanthurenic acid at 2ug i.v. did not increase Na⁺ excretion. However, subsequentadministration of synthetic xanthurenic acid 8-O-β-D-glucoside did causenatriuresis.

Example 5 Natriuretic Response to Synthetic Xanthurenic Acid8-O-β-D-glucoside (10 μg i.v.) in a Normal Sprague Dawley Rat

A female Sprague Dawley rat (250 g) was anesthetized lightly with etherand a tail vein catheter was placed using PE10 tubing. Additionally, aurethra catheter was inserted using KY jelly and 2% lidocaine as alubricant. The rat was restrained in a modified Plexiglas tube so thaturine could be collected in 1.5-mL microcentrifuge tubes. Salineinfusion started at time zero at 0.02 mL/min for the length of theassay. The same i.v. catheter was used to inject the test compound.Synthetic xanthurenic acid 8-O-β-D-glucoside, 10 μg i.v. was injected atthe time indicated in a 1-mL volume in saline over the course of 10minutes. At the indicated time the saline infusion was increased tenfoldto 0.2 mL/min for ten minutes and returned to 0.02 mL/min for theduration of the assay. The tubes were centrifuged at 14,000 rpm toseparate any RBC's from the urine. Na⁺ and K⁺ concentrations in theurine were measured with respective ion selective electrodes. The Na⁺and K⁺ excretion rates were calculated by: (vol of urine/time ofcollection period)×(ion urine concentration). Results are shown in FIGS.5-8. Synthetic xanthurenic acid 8-O-β-D-glucoside at 10 μg i.v. caused asustained natriuretic response in the normal rat. K⁺ excretion did notincrease in response to xanthurenic acid 8-O-β-D-glucoside. The initialnatriuretic response in FIG. 6 (10-20 min) was due to the increase inurine volume shown in FIG. 8, and not due to urine Na⁺ concentrationshown in FIG. 7. However by 60-90 minutes after administration thenatriuresis was due to the increased urine Na⁺ concentration as shown inFIG. 7.

Urine production decreased 140 min after administration resulting indecreased natriuresis. However when the saline infusion increased totenfold to 0.2 mL/min for 10 minutes, Na⁺ excretion rate increased from2 uEq/min to 10 uEq/min, seen in FIG. 6. These data are consistent withthe idea that xanthurenic acid 8-O-β-D-glucoside inhibited Na⁺reabsorption at the distal tubule causing Na⁺ excretion but only ifhydration and GFR were sufficient for enough fluid to reach the distaltubule.

Example 6 Natriuretic Response to Synthetic Xanthurenic Acid8-O-β-D-glucoside (10 μg) Followed by Furosemide (100 μg) in a NormalSprague Dawley Rat, (Oral Administration)

A female Sprague Dawley rat (250 g) was anesthetized lightly with etherand a urethra catheter was inserted using KY jelly and 2% lidocaine as alubricant. The rat was restrained in a modified Plexiglas tube so thaturine could be collected in 1.5-mL microcentrifuge tubes. No salineinfusion was administered. Synthetic xanthurenic acid 8-O-β-D-glucosidewas injected with a feeding needle at the time indicated in a 1-mLvolume of water over the course of 1 minute. Sixty minutes later 100 μgof furosemide was similarly administered with a feeding needle. Thetubes were centrifuged at 14,000 rpm to separate any RBC's from theurine. Na⁺ and K⁺ concentrations in the urine were measured withrespective ion selective electrodes. The Na⁺ and K⁺ excretion rates werecalculated by: (vol of urine/time of collection period)×(ion urineconcentration). Results are shown in FIGS. 9-12. Synthetic xanthurenicacid 8-O-β-D-glucoside (10 μg) was orally active by causing anatriuretic response in a normal rat. Sixty minutes after oraladministration, furosemide (100 μg) caused sustained Na⁺ excretion seenin FIGS. 9-11. Pretreatment with xanthurenic acid 8-O-β-D-glucosidefollowed by furosemide allowed increased Na⁺ excretion, but did notincrease K⁺ excretion in FIG. 10. Oral furosemide alone caused both Na⁺and K⁺ excretion (data not shown). Pretreatment with xanthurenic acid8-O-β-D-glucoside inhibited furosemide-induced K⁺ excretion.

Example 7 Natriuretic Response to Isolated Xanthurenic Acid8-O-β-D-glucoside (3 μg) Followed by Furosemide (20 μg) in UremicSprague Dawley Rat (i.v.).

Female Sprague-Dawley rat, weighing 225 g, was made uremic by tying offone kidney and 30-50% of the second kidney. Two weeks later the rat wasready to test for natriuretic activity. The rat was anesthetized lightlywith ether and a tail vein catheter was placed using PE10 tubing.Additionally, a urethra catheter was inserted using KY jelly and 2%lidocaine as a lubricant. The rat was restrained in a modified Plexiglastube so that urine could be collected in 1.5-mL microcentrifuge tubes.Saline infusion started at time zero at 0.02 mL/min for the length ofthe assay. The same i.v. catheter was used to inject isolatedxanthurenic acid 8-O-β-glucoside at the time indicated in a 1-mL volumein saline over the course of 10 minutes. After 2 hours 20 ug furosemidewas injected in the same manner. The tubes were centrifuged at 14,000rpm to separate any RBC's from the urine. Na⁺ and K⁺ concentrations inthe urine were measured with respective ion selective electrodes. TheNa⁺ and K⁺ excretion rates were calculated by: (vol of urine/time ofcollection period)×(ion urine concentration).

Results are shown in FIGS. 13-16. Isolated xanthurenic acid8-O-β-D-glucoside at 3 μg i.v. caused a sustained natriuretic responsein the uremic rat. The time course of Na⁺ excretion peaked at 70 minutesin the uremic rat shown in FIG. 13, which is a similar time course tothe synthetic xanthurenic acid 8-O-β-glucoside in the normal rat shownin FIG. 1. K⁺ excretion in FIGS. 14 and 15 did not increase in responseto isolated xanthurenic acid 8-O-β-glucoside. The diuretic response tofurosemide was classic in terms of its time course as well as the Na⁺excretion. Normally, furosemide also causes K⁺ excretion to the extentthat K⁺ supplementation is necessary in the clinical use of furosemide.A similar effect in normal rat is illustrated in FIG. 25 (furosemideonly). Pretreatment with xanthurenic acid 8-O-β-glucoside followed byfurosemide prevented the typical increase in K⁺ excretion in this assayshown in FIGS. 14 and 15.

Example 8 Na⁺ and K⁺ Urine Excretion Response to Isolated XanthurenicAcid 8-O-sulfate (2.0 μg) in Uremic Sprague Dawley Rat (i.v.Administration)

A female Sprague-Dawley rat, weighing 225 g, was made uremic by tyingoff one kidney and 30-50% of the second kidney. Two weeks later the ratwas ready to test for natriuretic activity. The rat was anesthetizedlightly with ether and a tail vein catheter was placed using PE10tubing. Additionally, a urethra catheter was inserted using KY jelly and2% lidocaine as a lubricant. The rat was restrained in a modifiedPlexiglas tube so that urine could be collected in 1.5-mLmicrocentrifuge tubes. Saline infusion started at time zero at 0.02mL/min for the length of the assay. The same i.v. catheter was used toinject the test compound. Isolated xanthurenic acid 8-O-sulfate, 2 μg,was injected at the time indicated in a 1 mL volume in saline over thecourse of 10 minutes. Then saline infusion was returned to 0.02 mL/minfor the duration of the assay. The tubes were centrifuged at 14,000 rpmto separate any RBC's from the urine. Na⁺ and K⁺ concentrations in theurine were measured with respective ion selective electrodes. The Na⁺and K⁺ excretion rates were calculated by: (vol of urine/time ofcollection period)×(ion urine concentration).

Results are shown in FIGS. 17-20. Isolated xanthurenic acid 8-O-sulfate(2 μg, i.v.) caused sustained natriuretic response in the uremic rat.The time course of the natriuresis peaked within 30 minutes and thenapproached control levels within 70 minutes of treatment, seen in FIGS.17 and 18. K⁺ excretion did not increase in response to isolatedxanthurenic acid 8-O-sulfate, shown in FIGS. 18 and 19.

Example 9 Na⁺ and K⁺ Urine Excretion Response to Synthetic XanthurenicAcid 8-O-sulfate (20 μg) in Normal Sprague Dawley Rat (OralAdministration)

A female Sprague Dawley rat (250 g) was anesthetized lightly with etherand a urethra catheter was inserted using KY jelly and 2% lidocaine as alubricant. The rat was restrained in a modified Plexiglas tube so thaturine could be collected in 1.5-mL microcentrifuge tubes. No salineinfusion was administered. Xanthurenic acid 8-O-sulfate was injectedwith a feeding needle at the time indicated in a 1-mL volume of waterover the course of 1 minute. The tubes were centrifuged at 14,000 rpm toseparate any RBC's from the urine. Na⁺ and K⁺ concentrations in theurine were measured with respective ion selective electrodes. The Na⁺and K⁺ excretion rates were calculated by: (vol of urine/time ofcollection period)×(ion urine concentration). Results are shown in FIGS.21-24. Xanthurenic acid 8-O-sulfate (20 ug) was not orally active withrespect to causing a natriuretic response in a normal rat. Inparticular, the Na⁺ urine concentration remained below 50 mM in FIG. 21whereas in i.v. administered xanthurenic acid 8-O-sulfate the Na⁺ urineconcentration increased from 60 mM to 160 mM in FIG. 19. In addition,Xanthurenic acid 8-O-β-D-glucoside was orally active in a normal rat byincreasing the Na⁺ urine concentration to 160 mM in FIG. 11.

Example 10 Protocol for Polyclonal Antibody Production AgainstXanthurenic Acid 8-O-beta-D-glucoside and Xanthurenic Acid 8-sulfate

The following protocol describes the production of polyclonal antibodiesto xanthurenic acid 8-O-beta-D-glucoside in the development of an ELISAassay to detect and measure xanthurenic acid 8-O-beta-D-glucoside inurine and plasma. Xanthurenic acid 8-O-beta-D-glucoside is covalentlylinked to the large protein KLH to elicit an immune response in rabbits.In addition, ASBA is used as a spacer arm (12 Å) between xanthurenicacid 8-O-beta-D-glucoside and KLH. The spacer arm allows betterpresentation of xanthurenic acid 8-O-beta-D-glucoside in the immuneresponse. In the screening of the antibody response, xanthurenic acid8-O-beta-D-glucoside is similarly linked to BSA which is then coatedonto ELISA wells. The rabbit serum is then screened for xanthurenic acid8-O-beta-D-glucoside antibodies by incubating the rabbit serum with theBSA conjugated to xanthurenic acid 8-O-beta-D-glucoside. These rabbitantibodies are detected by binding goat-anti-rabbit antibodies that areconjugated to the reporter enzyme horseradish peroxidase (HRP). Thesubstrate, tetramethylbenzidine (TMB) incubates with HRP and the productis measured at 400 nm.

Once the titer of the anti-serum against xanthurenic acid8-O-beta-D-glucoside is determined, urine samples are tested for thepresence of xanthurenic acid 8-O-beta-D-glucoside by competitive ELISAusing the specific polyclonal antibody. The validation of xanthurenicacid 8-O-beta-D-glucoside by ELISA will be done by the current HPLCmethod with fluorescent detection. This HPLC method was initiallydeveloped in the isolation of xanthurenic acid 8-O-beta-D-glucoside inhuman urine. The UV spectrum of xanthurenic acid 8-O-beta-D-glucosidecan also be examined in the urine samples. By the current HPLC method,the detection limit of xanthurenic acid 8-O-beta-D-glucoside in urine is2.7 uM with no solid phase extraction (SPE). SPE is expected to lowerHPLC detection limits to nM.

The clinical plasma and urine levels of xanthurenic acid8-O-beta-D-glucoside and xanthurenic acid 8-sulfate will be establishedby both ELISA and SPE/HPLC techniques.

1. A method for determining the amount of a compound of formula Ipresent in a human body fluid:

wherein R₁, R₂, R₃, R₅, R₆ and R₇ are independently X₃R where R isselected from the group consisting of H, halo; optionally substitutedsaccharide, aliphatic, cycloalkyl, aryl and heteroaryl;—P(O)(OR^(a))(OR^(b)) and —NR^(a)R^(b), where R^(a) and R^(b) areindependently H, optionally substituted aliphatic, cycloalkyl, aryl orheteroaryl; X₁ and X₃ are independently —C(O)O—, —OC(O)—, —C(O)NH—,—NHC(O)—, —OC(O)NH—, —NHC(O)O—, —OS(O)_(y)—, —S(O)_(y)—, —O—, —NHC(O)—,—NHC(O)O—, —S(O)₂NH—, a bond or absent; where y is an integer from 0 to3; R₄ is H, (═O); hydroxy; or optionally substituted saccharide,aliphatic, cycloalkyl, aryl or heteroaryl; or —P(O)(OR^(a))(OR^(b)) or—NR^(a)R^(b), where R^(a) and R^(b) are independently H, or optionallysubstituted aliphatic, cycloalkyl, aryl or heteroaryl; and X₂ is —O— andR₈ is optionally substituted saccharide; or X₂ is —OS(O)_(y)— or—S(O)_(y)—, where y is an integer from 0 to 3, and R₈ is H or optionallysubstituted aliphatic; the method comprising: a. obtaining a human bodyfluid b. measuring the amount of the compound of formula I in the humanbody fluid.
 2. The method of claim 1, wherein the compound of formula Iis xanthurenic acid-8-O-β-D-glucoside xanthurenic acid 8-O-sulfate.
 3. Amethod for monitoring or detecting a disease associated with an abnormallevel of xanthurenic acid-8-O-β-D-glucoside or xanthurenic acid8-O-sulfate, the method comprising: detecting a level of xanthurenicacid-8-O-β-D-glucoside or xanthurenic acid 8-O-sulfate in a biologicalsample, wherein an excessive or deficient of level of the compound offormula I in the biological sample is associated with the disease. 4.The method of claim 3, wherein an elevated level of xanthurenicacid-8-O-β-D-glucoside or xanthurenic acid 8-O-sulfate in the biologicalsample is associated with the disease.
 5. The method of claim 3, whereina deficient level of xanthurenic acid-8-O-β-D-glucoside or xanthurenicacid 8-O-sulfate in the biological sample is associated with thedisease.
 6. The method of claim 3, wherein said disease is selected fromthe group consisting of hypertension, edema, acute renal failure,congestive heart failure, chronic renal failure, ascites, increasedintra-ocular pressure, nephrotic syndrome or other disease stateinvolving irregularities in fluid/sodium balance.
 7. The method of claim3, wherein said biological sample is a urine sample.
 8. The method ofclaim 3, wherein said biological sample is a serum sample.
 9. The methodof claim 1, further comprising the step of monitoring or detecting adisease associated with an abnormal level of the compound of formula I.